MINRES crashes on seemingly valid example
Submitted by dab..@..rd.edu
Assigned to Nobody
Link to original bugzilla bug (#1558)
Version: 3.3 (current stable)
Operating system: Linux
Description
I am trying to solve the following system with the (ok, unsupported) MINRES module:
A =
[-2 1 0 0 0 0 0 0 0;
1 -2 1 0 0 0 0 0 0;
0 1 -2 1 0 0 0 0 0;
0 0 1 -2 1 0 0 0 0;
0 0 0 1 -2 1 0 0 0;
0 0 0 0 1 -2 1 0 0;
0 0 0 0 0 1 -2 1 0;
0 0 0 0 0 0 1 -2 1;
0 0 0 0 0 0 0 1 -2]
b =
[-98.1
-0
-0
-0
-0
-0
-0
-0
-0]
(all doubles here). The solver crashes with a floating point exception, looks like during a /= operation, so probably a divide by zero. However, this system should be solvable by MINRES (it's symmetric indefinite), and it does solve correctly using another MINRES implementation (not the one in Eigen). So this seems like a bug with the Eigen implementation. Does anyone have any ideas on what's going on here, and if there might be a way to fix the MINRES module? Thanks!